The invention relates generally to defibrillators and, more specifically, to defibrillator control.
Ventricular fibrillation is a common and dangerous medical condition that causes the electrical activity of the human heart to become unsynchronized. Loss of synchronization may impair the natural ability of the heart to contract and pump blood throughout the body. Medical personnel treat ventricular fibrillation by using a defibrillator to apply an electrical current to the heart. The current flow overcomes the unsynchronized electrical activity and gives the natural pacing function of the heart an opportunity to recapture the heart and reestablish a normal sinus rhythm.
The appropriate energy dosage for a particular patient depends on a number of variables, including the body structure of the patient. A larger patient, for example, may exhibit greater electrical resistance through the thorax, known as transthoracic impedance, than a smaller patient. As a result, effective treatment of large patients tends to involve larger energy dosages. Large energy dosages, however, may traumatize the heart and cause discomfort to the patient. Accordingly, the American Heart Association (AHA) recommendation is an incremental approach to electrotherapy in which the heart initially receives a lower energy dosage. If required, an operator may increase the dosage by increments. For example, the recommended initial energy dosage for a patient may be 150 joules (J). If this dosage is ineffective, the operator may increase the dosage to 175 J and, subsequently, 200 J by adjusting a dosage setting of the defibrillator.
Electrotherapy may vary not only the electrical energy dosage applied to a patient, but also the morphology of the energy dosage waveform. Biphasic defibrillation involves passing a relatively large energy dosage across the heart in one direction, followed by a smaller energy dosage in the opposite direction. The initial dosage for biphasic defibrillation tends to be smaller than an earlier initial dosage for monophasic defibrillation. Biphasic defibrillation may involve incrementally increased energy dosages. Nevertheless, biphasic defibrillation can achieve results that are comparable to earlier monophasic defibrillation with lower energy dosages and reduced trauma to the heart.
Variations in the dosage energy and pattern, as well as other operating parameters, may make operating a defibrillator difficult, particularly for non-medical or minimally trained persons. Ease of operation has become an especially significant concern with the advent of portable defibrillation devices designed for use by first responders, who typically have little or no training. Such devices improve the likelihood of patient recovery by facilitating early administration of defibrillation, but require often untrained responders to be able to operate a complex medical device under stressful conditions.
In general, the invention facilitates use of a defibrillator, such as an automated external defibrillator (AED), by allowing a user to select an energy protocol to be followed when the defibrillator administers therapy to a patient. More particularly, the defibrillator can be preprogrammed with multiple defibrillation energy protocols, or sequences of energy dosages, for delivery to the patient under appropriate circumstances.
Each energy protocol defines a sequence of energy dosages or levels to be applied during consecutive shocks. When the defibrillator is activated, the first, and typically lowest, energy dosage in the sequence is administered to the patient. The defibrillator then determines whether the first dosage was effective, that is, whether the patient was successfully defibrillated. If the first dosage was ineffective, a period of CPR is recommended to be undertaken in which the defibrillator administers the second dosage in the sequence to the patient. This second dosage is typically higher than the first dosage. The energy protocol may specify additional energy dosages to be applied if the first two dosages are ineffective, each followed by a period of CPR.
The invention may offer several advantages. Programming energy protocols into the defibrillator, for example, facilitates operation of the defibrillator by relieving an untrained or undertrained responder of the task of selecting individual energy dosages to be applied to a patient. With multiple energy protocols programmed, the defibrillator can be converted from one type of device, such as a pediatric defibrillator, to a different type of device, such as a high energy defibrillator, quickly. The versatility of the defibrillator is thereby enhanced. Furthermore, because the responder can select the energy protocol most appropriate for the needs of the particular patient, therapy may be more effective in comparison to some conventional defibrillators that lack the ability to deliver therapy in accordance with an operator-selectable regime.
In one embodiment, the invention is directed to a method in which at least two energy protocols are stored in a defibrillator. Each energy protocol comprises a sequence of energy dosages for application to a patient. A selected energy protocol is applied to the patient.
Another embodiment of the invention is directed to a method in which at least two energy protocols are programmed in a defibrillator. Each energy protocol defines a sequence of energy dosages for application to a patient. The energy protocols are stored in a memory associated with the defibrillator.
Other implementations include defibrillation systems that carry out these methods, as well as computer-readable media containing instructions that cause a computer to perform these methods. For example, in one embodiment, a defibrillation system includes a defibrillator and a memory communicatively coupled to the defibrillator. The memory stores at least two energy protocols. Each energy protocol comprises a sequence of energy dosages for application to a patient. The defibrillator applies a selected one of the energy protocols to the patient.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.